Neisseria gonorrhoeae (Gc) is the sole cause of gonorrhea. One of the major virulence factors in Gc is the Type IV pilus. The pilus is directly involved in natural transformation, twitching motility, autoagglutination, and evasion of the host immune system. The pilus is a complex assembly of many different proteins and thought to be exported through the secretin PilQ, a dodecameric protein ring. PilQ is necessary for expression of the pilus, and thereforepilQ null mutants are defective for all pilus-dependent activities. Little work has been done to determine whether this secretin is directly involved in any of these pilin-dependent activities. The goal of this project is two-fold. First, using a previously developed error-prone PCR saturation mutagenesis method, determine which PilQ domains are required for multimerization, localization to the outer membrane, and pilus expression. Second, usingpilQ mutants derived from the first step, determine whether PilQ is directly involved in pilus-related pathogenic activities including autoagglutination, twitching motility, and natural transformation. If PilQ is shown to be directly involved in some or all of these, further analysis will be performed to determine which residues and/or domains are necessary for these interactions.